Technical Field
The present application relates to a bearing implementation for a rotating electrical device, and more specifically to a bearing implementation for an electric motor having at least three bearings.
Background Information
Electric motors are typically mounted with a front and a rear bearing with the intended purpose of providing a stable rotating environment for the rotor, thus turning electrical power into mechanical power. These bearings typically are rolling-element bearings that carry load by placing rolling elements (e.g., bearing balls) between two bearing rings. To maximize efficiency and to minimize losses due to friction, the selection of bearings, specifically the size of bearing balls used in the bearings, is generally carefully taken into consideration in the engineering and design process. Selecting a bearing configuration with larger diameter bearing balls normally provides longer bearing life, due to the ability of the bearing balls to better handle the load when compared to a configuration of smaller diameter bearing balls. However, as ball diameter is increased, the efficiency of the motor generally will drop as a result of increased friction losses resulting from increased surface area contact arising from the larger ball diameter. Therefore, in the engineering and design process there is generally a compromise in the selection of ball size, in order to yield a final motor design that provides sufficient bearing life and that meets desired efficiency standards, e.g., minimum governmental efficiency standards.
Bearing degradation and failure is often cited as one of the main causes of failure in electric motors. Due to the nature of electric motors, when a failure occurs, it typically happens on the front bearing. The front bearing generally handles the majority of the load incident upon the motor, and therefore generally fails before the rear bearing. When the front bearing fails, the entire motor will come to a stop resulting in unscheduled downtime, causing a direct financial loss to the end user in a production or critical uptime environment. Further, in some cases, the laminations in the rotor and stator will be damaged due to their collision after degradation of the front bearing. Thus, the end user often suffers financial costs associated with repairing or replacing the motor, and other costs associated with the down time of the motor.